The present inventon is directed to a device for pressing a pile of sheets in a feeding unit or station such as the feeding station of a folder-gluer.
In folder-gluers known so far, the sheets are transferred from a feeding station to another station of the machine by conveyor means having a plurality of endless lower belts which are arranged underneath a pile of sheets which are to be introduced into the machine. These lower belts are operated with means for preventing passage of more than one sheet from the bottom of the stack which means include one or several frontal stops called gauges or gates each having a lower edge. The gauges are positioned so that the lower edge is spaced above the surface of the belt a distance equal to slightly more than the thickness of one sheet.
During processing of sheets of corrugated cardboard, it is often difficult to draw only the lowermost sheet from the bottom of the pile. This difficulty is due to the fact that it is hard to vertically adjust the lower edge of the gauge with regard to the thickness of the cardboard. This adjustment is quite easy when processing solid pasteboard or cardboard sheets. However, if the machine is processing corrugated cardboard, the operation becomes more difficult because while the thickness of the sheet may be constant, the sheets tend to curve and thus it does not lie in a single plane. As is obvious, the excessive bending of a corrugated cardboard sheet will cause difficulty with passage of the sheet below the gauges due to the effective thickness of the sheet being different at different locations. Thus, corrugated cardboard sheets cause problems at the feeding station.
Simple solutions have already been suggested to compensate for these inconveniences created by the corrugated cardboard sheets. One of the solutions recommends the use of a presser mounted on top of the pile of sheets to be introduced into the machine. This device acts along a plane which is defined by the gauges and presses the pile to thus flatten the sheets in the pile. Consequently, all the sheets in the pile will have the same thickness at the location of the gauge.
The device mentioned hereinabove is made of one or several counterweights mounted on guiding rails. These counterweights are freely movable along the guiding rails and shift downward toward the lower endless belts of the feeder when the sheets are introduced into the machine. When the feeder is to be resupplied with a new pile or batch of sheets, these counterweights have to be lifted manually and kept in their elevated position during the loading of a new pile into the feeding apparatus. This device is quite economical as it does not require expensive equipment to built the counterweight system. However, the loading of a new pile of large sheets into the feeder can be difficult. The operator has to use both hands to load the large sheets into the feeder since the pile is heavy and not easy to handle. Consequently, he cannot lift and hold the counterweights which act on the pile and simultaneously load the new batch of sheets into the feeder. This requires the operator to either request help from another person or to use several steps to load the sheets into the feeder. Because of these problems with loading new sheets into the pile, the production of the folded and glued boxes by the folder-gluer is disturbed or even slowed down.